The former 'X-Files' star tells Sathnam Sanghera she's sorry for not running off at the mouth a little more but she's just very, very tired:

By Sathnam Sanghera

Gillian Anderson squints at her reflection in the large mirror on the wall, runs a hand through the hair that was once famously red but is now dyed dirty blonde, strokes the perfect skin under her perfect blue eyes and remarks: "I look bloody awful."

There are many adjectives I might have used to describe how Anderson, once voted the sexiest woman in the world, looks this Friday evening. "Tiny", "poised" and "aloof" spring to mind. But "awful" is certainly not one of them. She yawns and stretches as extravagantly as a tired Labrador. "I'm sorry. I'm exhausted." Another yaaawwwn. "Just another four hours of rehearsals tomorrow."

A propos of nothing at all, she points to an ornament on a shelf in the office we are borrowing: "Oooh, look, there are some flowers stuck in a box of coffee beans," she says. A silence. Sleepily, she adds: "I'm surprised the room doesn't smell of coffee."

Another silence as I struggle to respond to this aimless wittering. "Sorry, sorry, I was trying to . . . " Yaaawwwn. "Let's do the interview. Yes, yes. Mmmmmm. Focus, focus. Interview."

Interview indeed. We are here to talk about the play in which Anderson is starring from next week: The Sweetest Swing in Baseball, by Chicago playwright Rebecca Gilman. It is being put on at the Royal Court (although, inscrutably, this interview is being conducted at the Old Vic) and tells the story of a successful painter who suffers a mental breakdown after receiving bad reviews for an exhibition.

I remark that the new play sounds like it was written specifically for Anderson: she is playing a character called Dana (and Anderson, of course, became famous for playing FBI special agent Dana Scully in TV sci-fi series The X-Files), and she has herself had more than enough experience of bad reviews (Anderson was recently savaged by the critics for her West End debut in What the Night Is For).

"Err, yeeeaaah," she drawls sceptically. Although she says "yeeeaaah" and "y'know" all the time, like a Californian teenager, it's surprising how very English she sounds most of the time. "I don't know if I would call them bad reviews. They weren't all that positive, but they weren't absolutely dreadful." If not absolutely dreadful, many were at least partially dreadful: The Daily Telegraph described the play as "a pure, unmitigated stinker"; The Observer said it was something "which could and should send people screaming from the theatre"; the FT complained that her performance was "woefully uninvolving".

Anderson scratches her calf, possibly in irritation. "I think, in the end, I kind of did what I set out to do - I got back to the stage after not doing it for 10 years and did a two-hander in the West End without keeling over on stage or completely humiliating myself."

It must have been stressful to get such reviews though? "It was interesting to see how it affected how I showed up everyday," she says. "You can either let it get you down or you can remind yourself that you have a responsibility to the audience and to yourself and just push on through. I think that the process of doing that was very rewarding and healing."

To be fair, these reviews were only as bad as reviews for her previous non-X-Files project were good: her performance as Lily Bart in The House of Mirth, Terence Davies' film adaptation of Edith Wharton's portrait of early 20th-century New York, collected superlatives such as "revelatory", "stunning" and "magnificent". Long- running TV series frequently ruin actors for anything else, but Anderson's star is quite a way from fading.

If her profile seems to have been low over the past year, it is largely because she has taken a lot of time off - something she was unable to do when she was battling aliens, slimy monsters and duplicitous government officials in The X-Files. By any standards she had an intense time during her 10 years on the hugely successful TV show: she married Clyde Klotz, an art director on the series; got divorced; had a baby daughter (nine-year-old Piper now lives in Vancouver with Klotz); and had several other complicated relationships with people on the show.

She started filming the series when she was 24 and was 34 by the time she finally hung up her badge, gun and autopsy goggles. By her own calculation, she spent 16 hours a day, 10 months a year on the set - not an easy task given her youth, the drama in her life and her apparently stormy relationship with co-star David Duchovny.

Has she seen Duchovny since the show ended? "I was in LA recently and we had lunch," she replies, curtly. How was it? "Very pleasant." A pause and then some elaboration: "You see, we were essentially married. We saw each other more than either of us saw our partners. And it was like any relationship - it had its ups and downs."

How does she feel about The X-Files now, two years after she left? "I feel that it was a mixed experience. I was expecting it to be more difficult to leave than it was. I didn't want to work again for such a long time afterwards. Just the thought of getting back on to a set seemed like the worst idea in the world. There's a certain incestuousness that takes place on a set, whether it's two months or nine years. It just wasn't tasty any more. But a few months ago, I started to feel like I wanted to get myself back into it." She stares at the box full of flowers and coffee, reflectively. "Yeeeaaah."

The past year has been a mixture of a little work (she has been writing a screenplay, called Speed of Light, which she also plans to direct and produce, and working for some African Aids charities) and a lot of leisure.

"I went to Africa a couple of times, for long periods. I travelled a lot in Europe. I was in the States and Canada. I did things that I don't normally allow myself to do." She explains that these "things" included hiring a history tutor. "There's a lot of stuff that I don't know," she declares. "It's mostly historical stuff. So the tutor taught me about the history between the Russian Revolution and the start of the second world war. Stuff that just wasn't in my brain."

Did it help? "Yeah, yeah. But I really had to study it. I had to go over my notes repeatedly - it's pathetic. My boyfriend has a brain like a bloody sponge - he takes in absolutely everything. But I don't. I feel quite retarded sometimes."

Anderson is being very hard on herself: she is a long way from being "retarded". Indeed, even half- asleep and beside herself with tiredness, as she is today, she is very articulate. And the gaps in her knowledge can be explained by her peripatetic education (at the age of two, her American parents took her from Puerto Rico to live in Crouch End, north London, and then took her to small-town America at the age of 11) and her rebellious adolescence (she was arrested on graduation night for trying to glue the locks shut at her Michigan school).

She now has homes in Los Angeles, Vancouver and London. And while saying that London "is feeling more and more like home", tells me her sense of identity is still all over the place. "It's tricky, y'know. My first words were in Spanish, I grew up as an English schoolgirl with American parents, being teased about being a Yank, and then I went to America and didn't feel like that was home either. I don't know whether I feel American or British."

She adds that she still doesn't feel like she has had time to grow up properly. "I've always thought that once I reach 36 I will be a grown-up - and that's coming this year. But when I stop and think about all the responsibilities in my life - family, work, houses, films - I wonder how an eight-year- old is doing it all." A rare smile. "It would be so nice to have recess in the middle of the day to play with my toys on the living room floor."

Maybe getting married again will make her feel more grown up. She is currently engaged to Kenya-born Julian Ozanne, who among other things was once an FT foreign correspondent. She apparently met him after he organised a safari holiday for her. The timing and location of the wedding have been a subject of tabloid rumour for months (will it be Italy, northern Kenya, Welwyn Garden City?) and it is the subject that Anderson is most cagey about. "Yes, we are going to get married," she snaps in response to a query. The curled top lip that seemed sexy earlier now just seems aggressive. When? "Dunno."

We move off the subject quickly. Asked about her future plans, Anderson explains that the next year will mostly be taken up with film projects: she will be acting in some, producing some and directing some. There are plans for another X-Files feature film, but she insists that she has "no interest in doing any more television". (In fact she doesn't even watch it.)

She yawns extravagantly once again - this time her mouth opens so wide that I swear I could stuff a whole copy of the FT into it. I can't help noticing how perfect her teeth are. "Err, sorry, I'm just too tired to talk," she says. "I usually run off at the mouth a bit more . . . I'm just . . . "

Too tired, I know. I suggest that now she is too tired to even say that she is too tired, we should perhaps part. Two minutes after leaving I realise I've left my pen in the room. As I go to retrieve it, I find the most exhausted woman in the world snoozing in her chair.